This question assesses effective classroom management techniques.
Ignoring the disturbance (B) can lead to the situation escalating.
Punishing (C) or sending students out (D) are reactive, confrontational measures that can disrupt the class further and damage the student-teacher relationship.
Giving a brief pause (A) is a subtle and professional technique. A sudden silence from the teacher often makes students aware of their own noise and brings their attention back to the lesson.
It allows the teacher to regain control calmly and non-verbally before continuing the lesson. It is the most effective first step in managing minor disturbances.